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GH5 to Alexa Conversion


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Sure; it depends on what you'd like. Fuji and BMD have very good, usable color. I personally will use P4K with GH5; I hope to have EC to do a production this summer. 8 bit is tricky; I'd prefer t

Emotive Color Version 3 Core LogC Details - Rewrote engine to work at 65x65x65, main files are now at eight times resolution (supporting files processed at that resolution) - Fine tuned mu

"GH5 V-Log and Hybid Log-Gamma are transformed to precisely match the color science of the Alexa, without compromise." "The GH Alex conversion completely transforms the GH5 image, addressing ever

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Some quick test frames from home movie footage I got this week using V-Log. First impressions are that it's having a very nice effect. Very natural and the management of the light is very cinematic. I haven't used an Alexa much but have used an Ursa mini 4.6k and Canon C200 a lot, and this kind of reminds me of the Canon Wide DR profile. I just threw a few clips on a timeline and spent a minute or so adjusting each frame so this is pretty much ungraded, just with the daylight LUT.

I'm looking forward to editing something together. I recently got hold of a Digital Bolex so I'm into colour and skin tones, and this looks very promising.

Lens was a EF Tamron 24-70 f2.8 with Metabones speedbooster. I also used a Tiffen Vari ND.

 

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Been trying out this conversion for the past few of days. I've only had the GH5 for a few months but I really am enjoying the color response and the highlight rolloff of this profile. I used the LogC conversion LUT, LogC to Rec709 and some temperature adjustments on this one. I've got the original V-Log to LogC frame below. I have not had the pleasure of using an Alexa but your conversion gives the GH5 a better starting point for grading in my opinion. Great work!

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That looks really good @jsmorris_,

What do you think of Soft? It is something of a dream starting point for me, as compared to Arri's 709.

I took a minute to dial in the grade on top of the EC Soft component applied to your LogC shot, attached are the shifts I made to LGG and the color wheels:

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17 hours ago, JeremyDulac said:

Has anyone been using HLG instead of vlog and found better tonality? @Sage which profile do you prefer hlg or vlog? Are there benefits to vlog over hlg if hlg is better for tonality?

For our purpose, I recommend V-Log. The conversion to Alexa space is more direct via the VLog route, which minimizes translation error. Technically, HLG uses a bit more bit depth and stores shadows linearly, but in practice they are both effective storage formats for the core sensor data and will get you to the same place (extremes of range preserved).

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40 minutes ago, jsmorris_ said:

@Sage I'll have to try that out in the coming weeks! And your adjustments really tighten the grade there. Thanks!

Its a solid grade starting point; simply a matter of how much/where to add contrast, and whether to add a color cast. For me, Arri's 709 in general starts with a little too much contrast for wide DR shots, and a bit anemic saturation. With static starting points, it is an interesting question as to which 'one-size' palette will be ideal

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@Sage So after finally caving and getting vlog and trying out a few clips. I am loving the way your lut responds to highlights and color. It is looking very nice. I was curious about what you called accelerated highlight roll off in the 700 ire range. Is it important that the highlights stay compressed around 700 ire after your lut is applied? Personally I like the look of your soft lut for a final delivery, with a few tweaks and grain added, so I am trying to understand your intent for the luts - do you see people using them for final delivery or do you expect people to do further corrections after? Just curious on why the highlights dont fill to the top of my ire...it looks fantastic, just really interesting. A lot of people talk about adding rolloff to their luts, but your seems to be far more precise and deliberate.

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The conversions place the noise floor around 0-5 IRE, and full white around 70 IRE, with the dynamic range effectively linear between them. With a high dynamic range shot, this may be an effective final look. Shots with lower dynamic range will likely benefit from a dialing in of luma to conform to cinema IRE placement. Earlier in this thread are examples of Sicario and Birdman with corresponding IRE graphs to demonstrate ideal low-light placement of IRE levels. To achieve a more pastel effect, Sicario uses capped IRE placement of full white at about ~70 IRE. Birdman, on the other hand, has a few notable moments where they allow light sources to reach 99 (the brightest elements captured by the Alexa sensor). GH5 has limited DR in V Log L, and GHa uses the Sicario 70 IRE upper cap.

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11 minutes ago, Sage said:

The conversions place the noise floor around 0-5 IRE, and full white around 70 IRE, with the dynamic range effectively linear between them. With a high dynamic range shot, this may be an effective final look. Shots with lower dynamic range will likely benefit from a dialing in of luma to conform to cinema IRE placement. Earlier in this thread are examples of Sicario and Birdman with corresponding IRE graphs to demonstrate ideal low-light placement of IRE levels. To achieve a more pastel effect, Sicario uses capped IRE placement of full white at about ~70 IRE. Birdman, on the other hand, has a few notable moments where they allow light sources to reach 99 (the brightest elements captured by the Alexa sensor). GH5 has limited DR in V Log L, and GHa uses the Sicario 70 IRE upper cap.

Ok cool! How do you recommend making added luma adjustments? If the scene contrast is lower, do you recommend just simply stretching the luma out to the 70 ire range like a higher contrast scene? Should I use primary or log controls? Also, I assume all further adjustment should be made after the lut?

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2 hours ago, JeremyDulac said:

Ok cool! How do you recommend making added luma adjustments? If the scene contrast is lower, do you recommend just simply stretching the luma out to the 70 ire range like a higher contrast scene? Should I use primary or log controls? Also, I assume all further adjustment should be made after the lut?

Right, all adjustments (apart from white balance) should follow the conversion. Using lift/gamma/gain or the luma curve, you can place different elements in the scene in accordance with cinema placement. Take a look at the scenes with corresponding IRE graphs, you will see that scenes of a given type reliably place things of a given category (bright window, lit face, darkest black) at the same IRE level. All movies share general properties (darkest areas in indoor/night scenes placing just above 0) and ranges for for given scenes (shadow to highlight placement for lit faces indoors/outdoors). You can create an IRE guide for your grade, to have a consistent look throughout the film.

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